The engineering arts have long-used elongated hollow tubes that traverse the walls of gas-stream-carrying ducts or chambers so that the tubes can deliver fine solids entrained in a carrier gas from a source exterior of the duct or chamber to a point interior of the duct or chamber. Such elongated hollow tubes are conventionally referred to as “lances.” Generally, lances have a bore through which the solids and carrier gases flow. The bore is in delivery communication with an exterior solid and gas feed source and is open, at a point interior of the duct or chamber, to effect delivery of the solid and carrier gas through the lance bore into the target gas stream.
A difficulty facing the practitioner is pluggage of the lance bore and bore opening(s). Pluggage is a problem when the fed material is a solid. Solids are usually fed as particles suspended in or carried by a carrier gas. When using multiple lances, if pluggage is suspected, the practitioner cannot determine which lance is plugged without inspecting each lance. Such lance-by-lance inspection is time consuming and can require shutting down the entire lance array to enable inspection. Thus, there is a need for a process and apparatus to enable monitoring each lance for pluggage so that the offending lance can be identified, removed from service and de-plugged, all without affecting the operation of the remaining lances.